In a global system for mobile communications (GSM) system supporting enhanced general packet radio service (EGPRS), the network can utilize different modulation coding schemes for downlink and uplink packet data transmissions to, for example, adjust to changes in link quality. While the network can directly measure link quality of the uplink packet data transmissions, the network uses link quality measurements reported from mobile stations to determine link quality of the downlink packet data transmissions. An EGPRS-capable mobile station can report link quality measurements to the network using different types of packet downlink ack/nack messages, such as an EGPRS PACKET DOWNLINK ACK/NACK message (for EGPRS mode) or an EGPRS PACKET DOWNLINK ACK/NACK TYPE 2 message (for EGPRS2 mode). In the case of downlink dual carrier operation in which the EGPRS-capable mobile station is receiving packet data transmission on both a primary carrier and a secondary carrier, link quality measurements for the secondary carrier are reported in an extension information element of the EGPRS PACKET DOWNLINK ACK/NACK message or the EGPRS PACKET DOWNLINK ACK/NACK TYPE 2 message.